Reversing valve for regenerative furnaces or the like



Patented Dec. 22, 1942 REVERSING VALVE FOR REGENERATIVE FURNACES OR THELIKE Henry R. Loxterman, Oakmont, Pa., assignor to Blaw-Knox Company,Pittsburgh, Pa., a corporation of New Jersey Application January 16,1942, Serial No. 427,006

Claims.

This invention relates to a valve for controlling the flow of wastecombustion gases and air from and to the checker chambers of aregenerative furnace such as a blast furnace, open-hearth furnace, orthe like.

Reversing valves for regenerative furnaces operating under blast haveheretofore generally included separate waste-gas and air-inlet valves,viz., a sliding-closure valve in the waste-gas flue from eachregenerative checker chamber to the stack, and a mushroom-type air-inletvalve in a branch from each waste-gas flue between the checker chamberand the sliding-closure valve. A typical example of this arrangement isdisclosed in Knox Patent 1,397,380. In operating an installation of thiskind, the waste-gas valves are opened alternately to a variable degreeto regulate the draft from the checker chamber through the stack andcontrol the gas pressure in the furnace, the air-inlet valve of eachchecker chamber being open when the waste-gas valve of the same chamberis closed.

Mushroom-type valves are subject to numerous serious objections,particularly when made relatively large in size. It is very difiicult tomake them fit perfectly in the first place, and continue to seatproperly after they have been opened and closed, even if a good fit isobtained initially. Mushroom-type valves, furthermore, cannot be placedas close to the main waste-gas flue as would be desirable, because ofthe danger of warpage when subjected to high temperature. This is thereason for installing the air-inlet valves in branches from thewaste-gas flue instead of in the flue itself. Waste gases accumulate inthe branches while the air-inlet valves are closed and they are, ofcourse, full of air at the moment of reversal, which is a furtherobjection. The use of mushroom-type valves has continued, however,despite the aforementioned objections because of the lack of anythingbetter and the necessity of separate air-inlet and wastegas valves topermit adjustable opening of the latter for the purpose of draftcontrol. While combined air-inlet and waste-gas valves have been knownheretofore, they have not been of such construction as to permit thecontrol of the How of waste-gases in the manner of a damper.

I have invented a novel reversing valve which entirely eliminates themushroom-type inlet valve, thereby obviating the aforementionedobjections; incorporates in, a single valve, provisions for controllingboth the waste gases flowing out from the checker chamber to the stackand, upon reversal, the air flowing into the checker chamber; and iscapable of damper action to control the flow of waste gases. In apreferred embodiment, I provide a valve seat adapted to be installed inthe lines between the checker chambers and the stack. A closure memberis slidable along the seat. The seat is provided with openings spacedtherealong, forming a waste-gas outlet and an inlet for the normal airsupply. The closure member is adapted to cover the outlet when properlypositioned. The outlet and inlet openings are so dimensioned and spacedthat the air inlet will be entirely closed when the closure has beenmoved to partially open the waste-gas outlet, and maintained closed whenthe closure is moved to open the outlet further. This permits operationof the closure member as a damper to regulate the size of the openingfor outflowing waste gases, thereby to control the furnace draft. Thespacing and dimensions of the openings, furthermore, are such that whenthe waste-gas outlet is covered by the closure member, the air inlet isuncovered or opened.

The air inlet is dimensioned for normal air supply, 1. e., from asuitable fan, blower, or any convenient source of air under appropriatepressure. I also provide means for enlarging the air inlet, should itbecome necessary under emergency conditions to operate the furnace undernatural draft, i. e., without means for supplying air under pressurethrough the inlet opening of the valve. Such means includes an auxiliaryor emergency inlet which is normally closed by an openable or removablecover. The emergency inlet is so positioned relative to the normal inletthat both are covered by the valve closure when it is positioned to openfully the waste-gas outlet. My invention thus permits continuedoperation of the furnace after failure of the normal source of air underpressure, by merely opening or removing the cover of the emergency airinlet and raising the valve sufficiently to cover the emergency airinlet each time it is necessary to stop the air flow. Further lift ofthe valve may be provided, to allow it still to be used as a damper inthe flue leading to the stack. It is much more important that thefurnace should not be shut down during the running of a heat, than thatall the refinements of control employed under normal conditions bemaintained continuously.

Further details, novel features and advantages of the invention willbecome apparent during the following complete description andexplanation which refer to the accompanying drawing illustrating thepreferred embodiment briefly outlined above. In the drawing,

Figure 1 is a partial longitudinal section through the waste-gas flue ofa regenerative furnace showing the reversing valve of my invention; and

Figure 2 is a sectional View taken along the plane of line IIII ofFigure 1 showing parts in elevation.

Referring now in detail to the drawing, a flue I0 extends to a stackport II from the end of a checker chamber (not shown) opposite thatwhich is connected directly to the furnace. The flue ID, of course,alternately conducts waste combustion gases from the checker chamber andentering air to the checker chamber. It will be understood that acomplete installation includes two flues such as that shown in ID, thegeneral arrangement being shown in the Knox patent above mentioned.

The flue I0 has an offset I2 near the port H. A valve seat I3 installedin the flue adjacent the offset has an upwardly extending portion I3aoverlying the latter and a lower portion I31) overlying generally thesection of the flue proper. The seat I3 may conveniently be a suitablecasting and is provided with water-cooling passages I 4 and supply anddischarge connections l5 for the cooling water. A hood or cap I6 closesthe space between the edge of the offset I2 and the seat I3.

The lower portion I3b of the valve seat I3 is provided with an openingI! conforming generally to the interior of a section through the flue I0and affording an outlet for waste combustion gases passing through theflue from the end of the checker chamber to the stack port II. The valveseat also is provided with an opening I8 providing an inlet for thenormal air supply. A housing I9 fabricated from plate i ously,constitutes a continuation of the duct 23.

As shown, the housing is open at the top and is provided with aremovable cover.

The valve seat I 3 also has an opening 2 above the opening I8 which isadapted to serve as a supplemental inlet for air under emergencyconditions. The opening 24 is normally closed by an openable orremovable cover 25. As clearly shown in Figure 1, the cover 25 issomewhat L-shaped in section, the lower portion overlying the open topof the housing IS. The cover 25 is secured to the valve seat I3 byscrews 26 so that it may readily be removed when desired. When the coveris removed, outside air may freely enter through both the openings I8and 24.

A valve closure 21 is slidable along the valve seat. The seat may have aplane face but as shown has a rib 28 around the several openingstherethrough to reduce the friction between the closure and the seat andto facilitate the making of a tight joint therebetween. The seat %3, asillustrated, is inclined from the vertical so that the weight of theclosure 27 tends to hold it against the seat. The closure may beentirely of metal, preferably hollow and water-cooled, with a planeface; or it may have a plane face on only those portions which engagethe seat, or the closure may be similar to those shown on the Knoxpatent aforementioned, comprising a panel of refractory materialassembled on a suitable frame and within an enclosure fabricated fromplate and structural sections. A pull rod 29 extends downwardly throughthe hood I6 and is connected to the top of the closure member. Anoperating cable 30 is secured to the pull rod by a suitable terminalfitting 3I adapted to cooperate with a cushioning spring 32 coiled aboutthe rod and adapted to be compressed between the fitting and the hoodI6.

It will be clearly apparent from the drawing that the valve closure 21is so dimensioned as to completely cover the opening I! in the valveseat l3, when in its lowermost position, i. e., when the fitting 3|bears against the spring 32. When the closure is in such position, asillustrated in solid lines, air from the fan or blower is deliveredthrough the duct 23, the housing I9 and the opening or inlet I8 into theflue ID, as illustrated by arrows 33. When the closure 21 of the valveillustrated is in its lowermost position, the closure of the other valve(not shown) is in position to permit the outflow of waste-combustiongases to the stack port II as indicated by the arrow 34.

When it is desired to reverse the flow of air and combustion gasesthrough the checker chamber, the valve closure 21 is shifted to theposition shown in chain lies thereby permitting outflow of the gases asindicated by arrow 35. At the same time, the closure of the other valveis lowered to shut off the flow of combustion gases therethrough andpermit the entrance of air. It will be observed from the drawing thatthe air inlet I8 is closed when the closure 21 is only partly raised andis maintained closed as the closure is raised farther. This result isobtained by reason of the vertical dimension of the inlet l8 and itsspacing from the waste-gas outlet I1. The degree to which the opening I!is uncovered may be varied within Wide limits without uncovering theinlet l8. Thus, when the valve closure 21 is in position to permitoutflow of waste combustion gases, it may be adjusted to regulate thefurnace draft and is effective at all times to maintain the air inlet I8fully closed.

If the normal supply of air should fail for any reason, it is imperativeto continue the furnace in operation nevertheless. In such an emergency,the removal of the cover 25 permits air to flow into the flue I0 throughthe openings I8 and 24 when the valve closure 21 is in its lowermostposition. Under these circumstances, reversal of the flow of air andwaste gases necessitates raising the closure 21 high enough to fullyclose the opening 24, and. the lowering of the other valve closure toits lowermost position.

In this way, the flow of air through both the openings I8 and 24 is cutoff while the opening I! is uncovered to permit outflow of combustiongases. Under these circumstances, the valve closure can serve as adamper to regulate the furnace draft only after it has been raised highenough to fully close the opening 26. The lack of this refinement ofcontrol, however, is negligible compared to the advantage of makingpossible continued operation of the furnace after failure of the normalair supply.

It will be apparent from the foregoing descrip tion and explanation thatthe invention is characterized by numerous advantages. The eliminationof mushroom-type valves avoids all the objectionable features incidentthereto, The use of a single valve for controlling both the incoming airand the outgoing combustion gases reduces the cost of regenerativefurnace installations and simplifies the control thereof. The principaladvantages of the invention, of course, are the ability to operate thevalve as a damper to control the outflowing combustion gases whilemaintaining the air inlet closed and the provision for admitting airunder natural draft through the auxiliary inlet as well as the normalinlet, after failure of the normal air-supply means.

Although I have illustrated and described but a preferred embodiment ofthe invention, it will be recognized that changes in the constructionand arrangement of parts disclosed may be made without departing fromthe spirit of the invention or the scope of the appended claims.

I claim:

1. In a reversing valve, a valve seat, a closure slidable along saidseat, said seat having an outlet therethrough for waste gases and aninlet spaced from said outlet for admitting normal air supply, saidclosure being dimensioned to leave said inlet open when positioned toclose the outlet and to close the inlet when positioned to open theoutlet partially, and a supplemental air inlet in said seat sopositioned as to be closed by said closure when the outlet issubstantially fully open, and means normally closing said supplementalinlet.

2. In a reversing valve, a valve seat, a closure slidable along saidseat, said seat having an outlet therethrough for Waste gases, an inletfor normal air supply and an emergency air inlet, said closure beingeiiective to open fully the normal air inlet when closing said outlet,to close said normal air inlet when partially opening said outlet, andto close the emergency inlet when substantially fully opening saidoutlet, and a closure for said emergency inlet removably secured to saidseat.

3. In a reversing valve, a valve seat, a closure slidable along saidseat, said seat having an outlet therethrough for Waste gases and aninlet spaced from said outlet for admitting normal air supply, saidoutlet having a dimension in the direction of closure travel muchgreater than that of said inlet and the outlet and inlet being sopositioned relative to each other that when the outlet is closed theinlet is fully open and when the outlet is partially open the inlet isclosed, and a supplemental air inlet normally closed by a removableclosure but positioned so as to be closed by said first mentionedclosure when said outlet is substantially fully open.

4. In a reversing valve, a valve seat, a closure slidable therealong,said seat having spaced openings including a waste-gas outlet, a normalair inlet and an emergency air inlet, said closure being dimension d tofully close said outlet while leaving said normal inlet open, to closesaid normal inlet when only partly opening said outlet, and to closesaid emergency inlet when substantially fully opening said outlet and anopenable cover for said emergency inlet.

5. In a reversing valve, a valve seat, a closure slidable therealong,said seat having spaced openings including a waste-gas outlet, a normalair inlet and an emergency air inlet, said closure being dimensioned tofully close said outlet While leaving said normal inlet open, to closesaid normal inlet when only partly opening said outlet, and to closesaid emergency inlet when said outlet is substantially fully open, anair duct leading to said normal air inlet, an opening in said ductadjacent said inlet for admitting air directly thereto under naturaldraft, and means normally closing said last-mentioned opening.

HENRY R. LOXTERMAN.

